Wells are generally drilled into subsurface rocks to access fluids, such as hydrocarbons, stored in subterranean formations. The formations penetrated by a well can be evaluated for various purposes, including for identifying hydrocarbon reservoirs within the formations. Formation evaluation may involve drawing fluid from a formation into a downhole tool. In some instances, downhole fluid analysis (DFA) is used to test the fluid while it remains in the well. Such analysis can be used to provide information on certain fluid properties in real time without the delay associated with returning fluid samples to the surface. Information obtained through downhole fluid analysis can also be used as inputs to various modeling and simulation techniques to estimate properties or behavior of petroleum fluid in a reservoir.
Fluids drawn from formations for evaluation can include fluids occurring naturally in the formations, such as hydrocarbons, as well as other fluids. These other fluids can include mud filtrate (the liquid portion of drilling mud). During drilling and testing operations, wells are often kept in an overbalance state with drilling mud to inhibit formation fluids from flowing into the wells. In this state, mud filtrate invades formations from the wellbores and solid particulates in the drilling mud form mudcake along the wellbores. The presence of mud filtrate in a fluid sampled from a formation can impact the efficiency and accuracy of analysis of the sampled fluid.